1. Field of the Invention
The present invention is concerned with a process for producing concentrated fructose using relatively low cost starting materials and processing steps. More particularly, the method of the present invention is based upon a newly discovered, selective, preferential biological utilization or metabolism of glucose in mixtures of glucose and fructose.
2. Description of the Prior Art
Fructose has always occurred in man's food systems since it is found in the free form in almost all sweet fruits and berries. About fifty percent of the dry matter of honey, the oldest sweetener known to man, is fructose. In recent years however, there has been an increasing interest in the use of fructose, as opposed to sucrose, in various foods. The reasons for this interest are many, including: (1) diabetics must avoid sucrose in their diet, and therefore the use of fructose provides an attractive alternative; (2) sucrose-containing snacks, especially those which remain long in the mouth, have proved harmful to teeth; (3) the safety of using the synthetic sweeteners such as saccharine and cyclamate, has been questioned; and (4) the less pleasant taste of the synthetic sweetners (side- and after-taste) is unpopular with many customers.
Fructose, being a reducing keto-hexose, differs considerably from the non-reducing disaccharide, sucrose, in many of its chemical and physical properties. Fructose is the most water soluble of all of the sugars, but is rather difficult to crystallize, because of the existence of a mixture of tautomers in solution at equilibrium. The sweetness of crystalline fructose is nearly twice that of sucrose, and it is known that mixtures of fructose and saccharine or cyclamate produces a synergistic effect that can be used to advantage, especially in dietetic drinks. Moreover, the use of fructose in special products as an alternative to sucrose is warranted by its partly insulin-independent metabolism, which makes fructose a desirable sweetener in diabetic diets.
While the advantages of fructose use in food systems are many, widespread fructose usage has been thwarted because of the relatively high cost thereof. For example, in 1980 fructose was up to four times more expensive that sucrose. The principal reason for this cost differential stems from the fact that it is very difficult to obtain highly concentrated and/or crystalline fructose. Typical conventional processes, such as fractional crystallization, are very tedious and expensive. Accordingly, while crystalline fructose and solutions containing pure or nearly pure fructose are highly desired by the food industry, and particularly the beverage industry, products are in short supply and relatively expensive.
Accordingly, there is a real and heretofore unsatisfied need in the art for an improved process which will yield concentrated fructose, either in the form of a concentrated solution or as crystalline fructose, at a cost which will make fructose more competitive with traditional sugar.